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Biography

My first research was in Nottingham's computer science department, working on how artificially intelligent (AI) agents should go about revising their beliefs upon learning new information. I completed my PhD on a related topic, using formal logic to model the evolving knowledge of AI agents.

After my PhD, I took up a postdoc at Macquarie University, Sydney, where I worked on the philosophy and logic of resource-bounded reasoning. (That's reasoning that's logical and mathematical, but subject to real-world restrictions of time, memory and patience - the kind of reasoning we do when we're trying to work through some difficult problem.)

Whilst in Sydney, I began working on metaphysical questions about truth and about how reality is ultimately made up. I now work in the philosophy department at Nottingham, writing about truth, knowledge, reasoning and paradox.

For me, the big questions are about how the world ultimately is, and how we can think and know about it. I like to approach these difficult questions by combining the logical, technical approach of mathematics and computer science with the inventiveness of philosophy.

Expertise Summary

I've published and given research talks in the following areas:

Metaphysics: Truth and truthmaking, constitution, facts and states of affairs, modality and counterpart theory, existence and absence

Teaching Summary

I will be on research leave (and so not teaching) throughout 2017-18 and autumn semester 2018-19.

The primary aim of my teaching is to enable students to think clearly and think for themselves; and to learn how to discern arguments and evaluate them logically. I also aim to improve students' discussion and presentation skills; and improve their ability to judge whether the conclusions people draw are justified by reasons or are mere opinion. These are highly valuable and transferrable skills, and enable students to function as good citizens beyond university. In my approach, historical and factual information is secondary. It is a means to introduce a wide range of theories and viewpoints to students, but knowledge of it is not a main aim of my teaching.

A key theme in my approach is that students should take responsibility for their own learning. (This is particularly important in the transition from A-level to university-level study.) By this, I mean not only that students must motivate themselves to do enough reading and other independent study; but also that they should form their own opinions about a philosophical argument, and then engage in a process of self-critique and discussion with others.

Research Summary

My current research centers around three themes:

​1. Thinking about the impossible

(a) An account of propositions as sets of possible and (non-trivial) impossible worlds. This allows an account of same-saying. It also explains how logically equivalent propositions can be distinct and hence how they can be made true by distinct entities.

(b) An account of epistemic possibility, which is non-trivial in the sense that not every set of sentences represents some epistemic/doxastic possibility, and non-ideal in the sense that some epistemic possibilities are logically impossible. The account can be used to give a semantics for 'knows' and 'believes' (and possibly other psychological attitudes).

I bring this work together in my book, The Impossible (OUP, 2014). A further book on the topic, Impossible Worlds, which I'll co-write with Franz Berto (Amsterdam), is under contract with OUP.

2. The Nature of Truth

This project sets out the metaphysical nature of truth. It seeks to explain the ontological basis of the property being true. Along the way, I'll explain three crucial aspects of truth:

The truth makers: the bits of the world responsible for making truths true (and for making falsehoods false). I develop an account of states of affairs for this purpose.

The truth bearers: the things that are true or false. I argue that propositions do this job, and I develop a metaphysical theory of what they are.

The truthmaking relationship between truthmakers and truthbearers. I give both a metaphysical and a formal logical characterisation of the relationship.

Along the way, I'll develop a response to the liar paradox (and other semantic paradoxes, such as Curry's paradox). The project is primarily metaphysical, but it takes in aspects of philosophy of language (theory of truth, propositions), philosophical logic (the liar paradox) and formal logic (truthmaker entailment).

I present this work in a book, What Truth Is (under contract with OUP).

​3. Making up the world

The metaphysics of making: how a lump of stuff makes up some thing (material constitution); how some parts get together to make a unified whole (composition); whether (and if so, how) bundles of qualities make up a particular.

Past Research

In my PhD thesis (2006), I developed a logic and modal semantics for modelling rule-based agents (of the type that are being developed in AI for commercial applications) with limited cognitive resources (memory & time in which to reason). I axiomatized the logic and gave a number of proofs: soundness & completeness and a complexity analysis (one problem is in NP, another in PSPACE). For the modal semantics, two particular results are of interest:

- Bisimulation in these models is identical to modal equivalence between states.